The time variation of the voltage across the discharge channel of a TE N2 laser has been studied experimentally by means of the Pockels effect, with particular emphasis on the factors which affect the statistical time-lag. Functional relations to the mean statistical time-lag of the gas pressure, the repetition rate of discharge, and the coupling capacitor of the trigger wire for preionisation are examined. An attempt to obtain travelling wave excitation is also made by the use of a glass plate whose width linearly varies, taking advantage of the fact that the statistical time-lag becomes negligibly small, and the formative time-lag varies along the discharge channel.